Ultralow Specific on-Resistance Trench MOSFET with a U-Shaped Extended Gate

Abstract

An ultralow specific on-resistance (𝑅on,sp) trench metal-oxide-semiconductor field effect transistor (MOSFET) with an improved off-state breakdown voltage (BV) is proposed. It features a U-shaped gate around the drift region and an oxide trench inserted in the drift region (UG MOSFET). In the on-state, the U-shaped gate induces a high density electron accumulation layer along its sidewall, which provides a low-resistance current path from the source to the drain, realizing an ultralow 𝑅on,sp. The value of 𝑅on,sp is almost independent of the drift doping concentration, and thus the UG MOSFET breaks through the contradiction relationship between 𝑅on,sp and the off-state BV. Moreover, the oxide trench folds the drift region, enabling the UG MOSFET to support a high BV with a shortened cell pitch. The UG MOSFET achieves an 𝑅on,sp of 2 mΩ•cm 2 and an improved BV of 216 V, superior to the best existing state-of-the-art transistors at the same BV level.